For the most part right now, the only difference between power plants or coolers is the amount of power/cooling they provide, and as long as you’re providing enough for the rest of the build, having excess doesn’t help. Most of the time, the stock power plant and coolers are fine. But some ships like the 350r for example, are pushing the stock power plant to it’s limit with the stock configuration, so if you replace the ballistic weapon with laser, the power needs are suddenly too much and you’ll need to upgrade the power plant. This website: https://www.erkul.games/live/calculator will show you whether you need to upgrade the power plant or coolers. If you do need to upgrade the power plant or coolers, Military Grade A is a popular choice since it’s high performance and has high component HP, and it doesn’t have a lot of downsides like it used to when stealth was a factor.
Have you tested lately with a friend to see if your detectible range changes when you click the stealth button? I was told that button doesn’t really do anything anymore but haven’t tested it in a long time. That’s good to know about the stealth power supplies powering up faster. I hadn’t thought about powering the whole ship down to be more stealthy and then powering back up quickly to strike. That’s a cool idea. I was thinking about getting a Razor EX or something for those times I want to scout a pvp area without being detected, so I’ll consider that when upgrading the components.